V. Bernshtam

Weizmann Institute of Science | weizmann · Department of Particle Physics and Astrophysics

We review spectroscopic methods developed for the determination of magnetic fields in high-energy-density (HED) plasmas. In such plasmas, the common Zeeman-splitting magnetic-field diagnostics are often impeded by various broadening mechanisms of the atomic transitions. The methods described, encompassing atomic transitions in the visible and ultra...

Spectroscopic measurements of the magnetic field evolution in a Z-pinch throughout stagnation and with particularly high spatial resolution reveal a sudden current redistribution from the stagnating plasma (SP) to a low-density plasma (LDP) at larger radii, while the SP continues to implode. Based on the plasma parameters it is shown that the curre...

Detailed analysis of both the line-intensity ratios and line shapes of the K-lines of elements of different abundances (Fe, Cr, Ni, and Mn) emitted from the stagnation of a steel wire-array implosion on Z, were used to determine the line opacities. While the opacities at the early time of stagnation appear to be consistent with a nearly uniform hot...

We report on the observation of a fast current switching from a Z-pinch stagnating plasma (SP) to a low density plasma (LDP) that resides at larger radii. A small-scale Z-pinch experiment, optimized for a symmetric and reproducible compression, is investigated by polarization sensitive spectroscopy (magnetic field measured by using the separation o...

Spectroscopic measurements of the magnetic field evolution in a Z-pinch throughout stagnation and with particularly high spatial resolution reveal a sudden current redistribution from the stagnating plasma (SP) to a low density plasma (LDP) at larger radii, while the SP continues to implode. Based on the plasma parameters it is shown that the curre...

This article is part of a study on non-postage marks issued by various Jewish parties and public associations for advertising or propaganda purposes. In this particular case, the authors turn their attention to the vignettes of Jewish political organizations, which they consider in the context of Russian political life at the end of the XIX and the...

The authors publish rare stamps, drawings for which were made by famous artists, members of the “Kultur-League” association Issakhar Ber Rybak, El Lissitzky and Iosif Chaikov.

The article describes old Jewish charity traditions and how it was carried out via cinderella stamps during the World War I and on the cusp of the 19th and 20th centuries. Such stamps and vignettes (non-denominated) were issued for gathering funds to support Jewish hospitals, schools, cheap dining, as well as to provide help for Jewish refugees and...

The article describes old Jewish charity traditions and how it was carried out via cinderella stamps during the World War I and on the cusp of the 19th and 20th centuries. Such stamps and vignettes (non-denominated) were issued for gathering funds to support Jewish hospitals, schools, cheap dining, as well as to provide help for Jewish refugees and...

The interaction of powerful sub-picosecond timescale lasers with neutral gas and plasmas has stimulated enormous interest because of the potential to accelerate particles to extremely large energies by the intense wakefields formed and without being limited by high accelerating gradients as in conventional accelerator cells. The interaction of extr...

Ionization-induced self-channeling of a ≤500 MW, 9.6 GHz, <1 ns microwave beam injected into air at ∼4.5×103 Pa or He at ∼103 Pa is experimentally demonstrated for the first time. The plasma, generated by the impact ionization of the gas driven by the microwave beam, has a radial density distribution reducing towards the beam axis, where the microw...

Results of the non-linear interaction of an extremely short (0.6 ns) high power (∼500 MW) X-band focused microwave beam with the plasma generated by gas ionization are presented. Within certain gas pressure ranges, specific to the gas type, the plasma density is considerably lower around the microwave beam axis than at its periphery, thus forming g...

The spectral structures of the Heα and Lyα groups of lines are strongly dependent on the electron temperature in the plasma, on the plasma charge state composition, and the presence of fast electrons. We analyze the effect of the various parameters on the features of the spectral structures, and demonstrate methods to determine electron-temperature...

The results of the characterization of large-scale RF plasma for studying nonlinear interaction with a high-power (~400 MW) short duration (~0.8 ns) microwave (~10 GHz) beam are presented. The plasma was generated inside a Pyrex tube 80 cm in length and 25 cm in diameter filled by either Ar or He gas at a pressure in the range 1.3–13 Pa using a 2 M...

(Experimental studies of a spherical converging shock wave (SW) interaction with preliminary formed plasma are presented. The SW was generated by an underwater electrical explosion of a spherical Cu wire array (radius of 15 mm, number of wires of 40, and wire diameter of 0.1 mm) supplied by 240 kA amplitude current pulse with rise time of ∼0.8 μs....

The RITS accelerator (5–11MV, 100–200kA) at Sandia National Laboratories is being used to evaluate the Self-Magnetic Pinch (SMP) diode as a potential flash x-ray radiography source. This diode consists of a small, hollowed metal cathode and a planar, high atomic mass anode, with a small vacuum gap of approximately one centimeter. The electron beam...

Converging shock waves in liquids can be used efficiently in the research of the extreme state of matter and in various applications. In this paper, the recent results related to the interaction of a shock wave with plasma preliminarily formed in the vicinity of the shock wave convergence are presented. The shock wave is produced by the underwater...

The results of visible spectroscopy of the plasma formed inside a copper capillary placed at the equatorial plane of an underwater electrically exploded spherical wire array (30 mm in diameter; 40 wires, each of 100 μm in diameter) are reported. In the experiments, a pulsed power generator with current amplitude of ∼300 kA and rise time of ∼1.1 μs...

The experimental results of a promising pulsed plasma source, producing electron beams with a current density of up to 10 ${rm kA}/{rm cm}^{2}$ are presented. The beam duration was up to ${sim}{rm 1}~mu{rm s}$ , in an accelerating voltage of up to ${sim}{rm 350}~{rm kV}$ , without shorting of the cathode–anode gap by the cathode plasma. This plasma...

The difference between the ion thermal and effective temperatures is investigated through simulations of the Ne gas puff z-pinch reported by Kroupp et al. [Phys. Rev. Lett. 107, 105001 (2011)]. Calculations are performed using a 2D, radiation-magnetohydrodynamic code with Tabular Collisional-Radiative Equilibrium, namely Mach2-TCRE [Thornhill et al...

The results of experiments on the reproducible generation of electron beams in a vacuum diode supplied by a high-voltage pulse with amplitude of a 300 kV and duration of 600 ns are presented. A cathode based on carbon-epoxy capillary structure was used for generation of electron beams with current density of up to 5 kA/cm 2 . It was found that th...

form only given. Even though the physics of Z-pinch systems is understood in general, there is a severe lack of detailed experimental data on the thermalization processes and dynamics that govern the pinch behaviour, and on the plasma parameters during the stagnation phase. Here, we report on a novel spectroscopic system, used to determine temporal...

Оригинальный стиль, объединяющий бронзовые, медные, а также латунные предметы культового и бытового предназначения, получил у западных коллекционеров название «исраилиана» (Israeliana). Его характерной чертой является обращение к традиционным формам и мотивам еврейского искусства, которое мастера — выходцы из разных стран могли изучать по археологи...

Detailed spatially resolved spectroscopic analysis of a neon gas puff Z pinch on the Weizmann 1MA generator [1,2] indicates that the radius of the K-shell regions grows to a maximum and then decreases during the radiation pulse -- the opposite of that calculated by 1D-RMHD models. Here we compare Mach2 2D-RMHD [r-z, high resolution, moving grid, no...

Experiments are being performed on the Self-Magnetic Pinch (SMP) electron beam diode on the RITS-6 accelerator at Sandia National Laboratories. This diode produces a tightly focused electron beam (< 3mm diameter) which is incident on a high atomic number bremsstrahlung x-ray converter. Typical diode parameters are 120 kA, 7 MeV, and 70ns current pu...

Using time-resolved emission spectroscopy at visible wavelengths, we explored the conditions of plasmas generated by current-driven explosions of single aluminum wires. The experiments were carried out with 15 μm aluminum wires driven by the Low Current Pulser 3 (LCP3) at Cornell University.The plasma conditions were studied as a function of time a...

The results of experiments on the reproducible generation of an electron beam having a high current density of up to 300 A/cm2 and a satisfactorily uniform cross-sectional distribution of current density in a ∼200 kV, ∼450 ns vacuum diode with a carbon-epoxy capillary cathode are presented. It was found that the source of the electrons is the plasm...

We are initiating an experiment in which time resolved visible spectroscopy will be used to characterize the plasma in and near the minidiode in aluminum (Al) X pinches. The goal of the experiment is to determine the magnetic field and other plasma conditions near the outer radius of the imploding z-pinch in the minidiode. At this location the cond...

form only given: The thermalization and energy conversion to radiation in high-energy-density plasma is a topic of broad interest in laboratory plasmas and in astrophysics. Knowledge of the ion temperature is of decisive importance, since this parameter determines the rate of various processes, including that of the energy transfer to electrons. We...

The process of electron beam interaction with metal targets was characterized using electrical and optical diagnostics. Electron beams with current density of 5–10 A∕cm2, electron energy up to 120 keV, pulse duration up to 200 μs, and cross-sectional area of 8–30 cm2 at the target surface were generated by GESA I and GESA II facilities. Streak imag...

We are studying plasmas created by exploding aluminum wires on the 10 kA Low Current Pulser LCP3 at Cornell University, employing both high- and low-resolution time gated emission spectroscopy at visible wavelengths to determine the plasma parameters as a function of radial position and time. With high spectral resolution, we can determine the elec...

The self magnetic pinch (SMP) electron beam diode is being investigated as an intense flash x-ray radiographic source. The diode produces a focused e-beam (<3mm diameter) at 7 MeV and 150kA with a 45ns FWHM pulsewidth. Since the vacuum gap is small (˜ 1cm), plasmas formed on the electrode surfaces affect the diode impedance, x-ray spectrum, pulsewi...

The observation of Doppler splitting in K-shell x-ray lines emitted from optically thin dopants is used to infer implosion velocities of up to 70 cm/μs in wire-array and gas-puff Z pinches at drive currents of 15-20 MA. These data can benchmark numerical implosion models, which produce reasonable agreement with the measured velocity in the emitting...

The time history of the local ion kinetic energy in a stagnating plasma was determined from Doppler-dominated line shapes. Using independent determination of the plasma properties for the same plasma region, the data allowed for inferring the time-dependent ion temperature, and for discriminating the temperature from the total ion kinetic energy. I...

form only given.We present detailed analysis of the implosion dynamics and stagnation of a Stainless Steel wire array z-pinch on the Z generator. Z2011 was a 0.68mg/cm, 70mm on 35mm nested wire array. In this presentation we use the complete set of data available for this shot to discuss in detail the implosion dynamics and conditions in the final...

form only given. The conditions within plasmas generated by current-driven explosions of single 15-50μm aluminum (Al) wires are being investigated using time-resolved emission spectroscopy at visible wavelengths. The experiments are being carried out at Cornell University on the 10kA, 500ns rise time Low Current Pulser 3 (LCP3). The plasma paramete...

We are exploring the conditions of plasmas generated by current-driven explosions of single fine aluminum wires, including temperatures, electron density, ionization state, and potentially magnetic field, using time-resolved emission spectroscopy at visible wavelengths. The experiments are being carried out with 15mum to 75mum Al wires driven by th...

Fast z-pinches provide intense 1-10 keV photon energy radiation sources. Here, we analyze time-, space-, and spectrally- resolved ˜2 keV K-shell emissions from Al (5% Mg) wire array implosions on Sandia's Z machine pulsed power driver. The stagnating plasma is modeled as three separate radial zones, and collisional-radiative modeling with radiation...

We study warm dense matter formed by subpicosecond laser irradiation at several 10(19) W/cm(2) of thin Ti foils using x-ray spectroscopy with high spectral (E/DeltaE approximately 15,000) and one-dimensional spatial (Deltax=13.5 microm) resolutions. Ti Kalpha doublets modeled by line-shape calculations are compared with Abel-inverted single-pulse e...

Parameters of the plasma produced by a ferroelectric plasma source �FPS� assisted high-current ��1 kA�, hollow anode �HA�, low-pressure �10−4 Torr� Ar gas discharge were studied using a time- and space-resolved laser induced fluorescence �LIF� diagnostic technique. It was shown that the plasma filling of the HA cavity occurs due to the expansion of...

Fast z-pinches provide intense 1-10 keV photon energy radiation sources. Analysis of time-integrated K-shell x-ray spectra indicates electron temperatures up to 5 keV and ion densities of order 10^20 cm-3 in the stagnated plasma created from wire array implosions on Sandia's Z machine pulsed power driver. Elliptical crystal spectrometers coupled to...

In the last few years, various intriguing emission profiles have been observed in time-gated, radially resolved measurements of K-shell line emission from imploding and stagnating Z-pinch plasmas. The radially resolved lines have appeared as hollow or closed ovals whose extents in the spatial and (Doppler-shifted) wavelength dimensions record the p...

The results of time- and space-resolved spectroscopic studies of the plasma produced at the surface of the ferroelectric cathode during the operation of an S -band relativistic magnetron generating ∼50 MW microwave power at f=3005 MHz and powered by a linear induction accelerator (LIA) (150 kV, 1.5 kA, 250 ns) are presented. The surface plasma was...

In this report we present results of comparison of experimental research of the relativistic magnetron operation with commonly used explosive emission plasma cathode and novel ferroelectric plasma source (FPS) cathode. The experiments were carried with relativistic S-band magnetron powered by linear induction accelerator (LIA) (~350 kV, 4 kA, 200 n...

Summary form only given. Full understanding of the dynamics, population kinetics, and energy budget of a K-shell radiating Z-pinch remains a challenging problem in high energy density plasma physics. Recently, detailed axially-imaged spectroscopic measurements were performed on a Ne gas puff driven by the Weizmann generator (500 kA in 500 ns). The...

Experiments have been conducted at Sandia National Laboratories' RITS-6 accelerator facility (operating at 7.5 MV and 180 kA) investigating plasma formation and propagation in relativistic electron beam diodes used for flash X-ray radiography. High resolution, visible and ultraviolet spectra were collected in the A-K gap of the self-magnetic pinch...

Radiative cascades into autoionizing states 1s2l2l in Li-like ions are studied. The correction function that describes the effect of cascades on level populations is calculated using the 1/Z -expansion method for the range of nuclear charges Z = 10–30. It is shown that for the q-satellite, which is often used in hot plasmas for diagnostic purposes,...

We show that the criticism [Eur. Phys. J. D 49, 167 (2008)] of our empirical formula for electron-impact ionization of atomic ions [J. Phys B. 33, 5025 (2000)] is unjustified.

Excitation of Al / Al ₂ O ₃ microplasma devices with 50 μ s , 800 V pulses produces, in Ar / H ₂ gas mixtures at 600 Torr, ∼6 A current pulses with a duration of ∼30 ns . Corresponding to peak current and power densities of ∼10⁴ A / cm ² and ∼2.5 GW / cm ³ , respectively, these pulse...

Experiments are being conducted to investigate fine wires as potential plasma sources for applications such as intense electron beam transport and propagation. For these studies, a microsecond long, low inductance, capacitive discharge (40kA, 50kV) is driven through a wire(s) to generate a plasma. The plasma expansion is determined by JxB forces wh...

Results of a time- and space-resolved spectroscopic research studies of an S -band relativistic magnetron generating 1.5×10⁸ W microwave power at f=2950 MHz , powered by a linear induction accelerator (450 kV, 4 kA, 150 ns), are presented. The cathode plasma electron density and temperature were obtained by analyzing H _α and H...

We present spectroscopic measurements in which utilized are line-intensity ratios in the near-uv to measure electron energies of several hundred eVs, which usually necessitates the use of emission in the soft x-ray region. The main intensity ratio selected is of the BIII transition 1s(2)2s2S(1/2)-1s(2)2p2P3/2 (2066A) and the BIV transition 1s2s3S(1...

Results of optical and spectroscopic studies of the plasma formation at the surface of two types of carbon-fiber cathodes in a diode powered by an ~200 kV accelerating pulse are presented. It was found that during the pulse, generation of the plasma occurs in a form of several millimeter size plasma spots. In the vicinity of the cathode surface the...

Summary form only given: A series of experiments were conducted at Sandia National Laboratories on the RITS-6 accelerator configured in the low impedance mode (7.5 MV, 180 kA) to investigate electrode plasma formation and propagation in relativistic electron beam diodes used for flash x-ray radiography. In particular the Self- Magnetic Pinch diode...

Summary form only given. The time-history of the ion-kinetic energy Ek ion throughout the stagnation phase of a neon-puff, 500 ns, 600 kA, Z-pinch implosion was determined. The X-ray spectroscopic system provides a resolving power of 6700 and four consecutive time gated (~1 ns) spectra. A simultaneous axial imaging allows for studying the ion kinet...

Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spec...

Thomson scattering and visible spectroscopy were applied to study the parameters of plasma formed in a hollow-anode discharge (about 1 kA) prior and during electron beam extraction (approximately 1 kA; 300 kV). The discharge was ignited and sustained by ferroelectric plasma sources incorporated in the hollow anode. It was found that during the holl...

The ion-kinetic energy throughout K emission in a stagnating plasma was determined from the Doppler contribution to the shapes of optically thin lines. X-ray spectroscopy with a remarkably high spectral resolution, together with simultaneous imaging along the pinch, was employed. Over the emission period, a drop of the ion-kinetic energy down to th...

Determination of z-pinch implosion velocity and thus coupled kinetic energy is key to understanding energy balance in wire array radiation sources. We discuss diagnosis of velocity via observation of Doppler shifts in K-shell lines for Al implosions on the 20 MA Z machine. For a small-mass load, classic oval-shaped Mg dopant lines are observed with...

We study the higher-subshells effect on the direct ionization from inner 1s, 2s, 2p, 3s, 3p subshells of ions charged 5+ and more. The cross-sections analysed are those calculated in the relativistic distorted-wave (RDW) approach. For removal of an electron from a certain nl-subshell of ions, belonging to a sequence of ionization stages, we found a...

We report on an experimental study of a channel spark discharge CSD and the generated electron beam. The CSD was operated at a discharge voltage U d 30 kV and a discharge current I d 3.5 kA. The CSD system consists of a glass tube placed between a hollow cathode and a grounded anode electrode. The parameters of the CSD operation, the potential dist...

An investigation of the properties of the plasma and the electron beam produced by velvet cathodes in a diode powered by a 200 kV, 300 ns pulse is presented. Spectroscopic measurements demonstrated that the source of the electrons is surface plasma with electron density and temperature of 4 10 14 cm −3 and 7 eV, respectively, for an electron curren...

The time-dependent radial distributions of the electron and ion densities during the implosion phase of a gas-puff z-pinch plasma are determined from measurements of continuum radiation, as well as time-dependent collisional-radiative analysis of the observed particle ionization history in the plasma. It is shown that during the 140‐ns-long time in...